Crit confirmed but max damage had already been achieved on the strike.
The crit table indicates we do not get double dmg but do achieve max dmg.
The original roll for dmg in my post already maxed the initial dmg from the strike.
Should i make another roll for dmg or ???

When the crit cart states double damage, that's it's wording for doing the x2 crit damage, in addition to the additional penalty. SO yes, you should be rolling an additional set of damage dice and adding it.

(EDIT: Oh.. sorry - forgot about the houserule changing that - honestly never even noticed that before).

The idea of this house rule was to underwhelm...
I don't think the difference in damage is really that big since whenever the card tells you to deal double damage, you basically deal the average of that (I think... I'm very bad at math). Though you don't get the benefit of dealing more than average, you also don't take the risk of dealing less than that.

If you think its unfair, I don't mind changing it to doing exactly whats on the card, or give up on the whole cards idea and just do double/triple damage on the criticals and miss on a roll of 1.

I just think its a bit of shame that a combat that was supposed to be dramatic will be over in two rounds because a player or two lucked it with the criticals.

It's just sort of a double penalty on the high multiplier weapons. The offset for them having lower threat ranges, and thus getting crits less often is that when they do, the damage is higher. With the cards standard rules, this is already a bit penalized, because even x3 and x4 weapons still typically only do double damage + condition, same as a high threat range weapon. The ability to draw a couple cards is not usually enough of an offset for that. To remove even the double damage means that is even more of a disparity.

One of the optional rules on the card is that instead of the multi-draw aspect, an x3 weapon increases the damage by one multiplied over what the card says (so if the card does normal damage, it does x2 with an x3 weapon, if the card does double, it does x3 on the x3 weapon, and so on). An x4 weapon increases the card's multiplier by 2 steps.